Mix yeast, sugar and water so that the sugar and yeast dissolve then allow to sit until the mixture bubbles, around 5-10min.
Meanwhile, mIx flours, thyme, lemon zest and once bubbled-up, add the yeast water. Mix to combine, tip out onto a floured surface and knead for around 5 min (stretching the dough out, folding over, turning 90 degrees and repeating) until the dough is no longer sticky.
Lightly oil a large bowl, put the dough in and leave to prove for around 1 hour until it has doubled in size.
Tip out the dough, press down to take out the air, divide in two (if you want two loaves, as I'd suggest) and stretch them out relatively flat. Form slightly as you prefer. You can also form directly on the baking sheet/tray.
Lay on oiled baking sheet/tray(s), either tossing in the oil or drizzling a little more on top to get on both sides. Allow to rise again for around 20min.
Preheat oven to 425F/210C.
Make finger marks on top, sprinkle on some more thyme, and a little salt, and drizzle over a little more oil so it sits in the dimples.
Bake for approx 20min until golden on top and it sounds hollow when tapped on the bottom.
Remove from oven and transfer to a cooling rack. Allow to cool a few minutes before cutting.